S Davis
Solar Enthusiast
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- Sep 25, 2021
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If you have room for a small fan you can locate the heating pad on the bottom or side walls of your enclosure, I just used the bottom because I had room from the vibration isolators.
LiFePO4 heating pad for cold temperatures
- Thread starter Will Prowse
- Start date
I know this is an older post but I'm curious on your battery box setup. What controller are you using for the heating pad?
These ones:
You can find them on Amazon and the like:
Horsefly
Solar Wizard
I would add that for those of us (like me) that are too backwards to think in Celsius, Amazon has several thermostatic controllers that use °F instead of °C. I used a couple of these for my 24V battery: https://www.amazon.com/gp/product/B076YD8H19
Others here have used the 12V model: https://www.amazon.com/LM-YN-Thermostat-Fahrenheit-Temperature/dp/B076Y5BXD9
The ones that @upnorthandpersonal linked to are cheaper and look better (with an enclosure), so if you can think in Celsius, they are a good choice (for 12V systems).
Others here have used the 12V model: https://www.amazon.com/LM-YN-Thermostat-Fahrenheit-Temperature/dp/B076Y5BXD9
The ones that @upnorthandpersonal linked to are cheaper and look better (with an enclosure), so if you can think in Celsius, they are a good choice (for 12V systems).
I have the thermostats that Horsefly linked to. I prefer the Fahrenheit version. My only gripe about them is that the four terminals that we connect to (power and relay) are wimpy. They don't do a great job of holding onto the wires.
Horsefly
Solar Wizard
I put ferrules on the wires, then the screw-down contactors hold well.
Kristof
1977 Airstream Off Grid Trailer
Two winters later . . .
Last year did not go so well. really low temps (-15 cel) and the watts the heating pad through out was not enough to keep up. Fortunately the BMS did and I switched to the lead carbon bank to maintain the heaters below zero. Seems to be the only way as the BMS shuts off the discharge power below zero, so no juice for the heating pad. I have played with a number of settings but he real kicker is to keep the snow off the panels or everything shuts down. Also I have about 50 watts of heat go into the aluminum on the bottom of the batteries but that draws constant when it is really cold. The best solution I can find here in Colorado is to keep the lead carbon bank on, LiFePO4 bank off and let the LC bank keep the Lithium bank from freezing. They are enclosed with some insulation but when the trailer is not heated and the wind blows outside, it is really hard to keep the Lithium warm enough to stay over zero. This year I check every week and the problem seems to have not gone away. At the end of the day it is about balance between your solar array and the power to keep the lithium bank warm enough.
Last year did not go so well. really low temps (-15 cel) and the watts the heating pad through out was not enough to keep up. Fortunately the BMS did and I switched to the lead carbon bank to maintain the heaters below zero. Seems to be the only way as the BMS shuts off the discharge power below zero, so no juice for the heating pad. I have played with a number of settings but he real kicker is to keep the snow off the panels or everything shuts down. Also I have about 50 watts of heat go into the aluminum on the bottom of the batteries but that draws constant when it is really cold. The best solution I can find here in Colorado is to keep the lead carbon bank on, LiFePO4 bank off and let the LC bank keep the Lithium bank from freezing. They are enclosed with some insulation but when the trailer is not heated and the wind blows outside, it is really hard to keep the Lithium warm enough to stay over zero. This year I check every week and the problem seems to have not gone away. At the end of the day it is about balance between your solar array and the power to keep the lithium bank warm enough.
JBennettBus
New Member
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- Oct 6, 2022
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I plan to remain south of Colorado until things warm up a bit, but the idea of a second battery bank is interesting. Well, a second battery in my case. I replaced 3 gel batteries with one LifePo4, and although the gel batteries still have some life in them, I haven't been able to give them away. Maybe I'll put one back in my bus as a heater battery to keep the lithium comfy. Probably wouldn't work in the conditions you're dealing with, but maybe it'd be enough for nights that don't get too far below freezing.
Daddy Tanuki
Solar Wizard
so in the middle of the second winter for my setup, 16 25 watt pads wired in series parallel to get the output I want with no controler. the original setup had a controller but with all the controllers being 12, or 24 volts i was using a 48/12 relay to work between the controller and the heating pads and the relay kept burning its contacts, probably due to the fact that the pack is 54~55 volts and the relay is listed as 48 volt capacity this is the second one to burn out on me.
battery pack varies between 8°c and 15°c I had been datalogging it with a pair of 4 channel temp loggers but after 2 months I stopped logging and now only spot check in the early morning and at mid after noon to see how much swing I have from low to high. with 8 thermal probes spread out through the pack the data is pretty clear.
this is a 35kw bank with 5.6kw of panels due south at 45° angle and 1.6kw of panels vertical facing west to lengthen out the solar day.
battery pack varies between 8°c and 15°c I had been datalogging it with a pair of 4 channel temp loggers but after 2 months I stopped logging and now only spot check in the early morning and at mid after noon to see how much swing I have from low to high. with 8 thermal probes spread out through the pack the data is pretty clear.
this is a 35kw bank with 5.6kw of panels due south at 45° angle and 1.6kw of panels vertical facing west to lengthen out the solar day.
Racoon Dog,
Wow!! Very impressive.
I keep burning out controllers (2 of the cheapies) on a 12v heating pad. 300 watt panel on the roof of my Promaster, 4 cell battery.
Wonder how much damage I have done to the battery?
Old Toad
fratermus
Solar Enthusiast
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- Mar 19, 2021
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The inkbird-type controllers are very reliable. They are popular in homebrewing and egg incubation applications where failure would be Very Bad.
Thank you very much.
Sanwizard
Solar Wizard
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- Feb 2, 2021
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- 2,715
What about the FACON pads that are used underneath RV's to keep the tanks warm? They are set to above freezing, and work automatically when it gets cold. 12V, and I know Will covered these in an upload a while back.
Got one but I heard there were problems with the thermostat.
Thought the controller would be better.
Ordered a Inkbird off the a'Zon, cheaper, better reviews than what I was considering.
Leeds
Solar Enthusiast
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- Jul 7, 2022
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It appears as though you were targeting 38-42° as your minimum battery temp.
In retrospect would targeting 34-36° have allowed you to ride through long enough? Or was snow load a multiple day event that would have failed either way?
I talked with one of the companies that makes the RV pads, but not the one in your link. They warned me to not use those on a battery. They're configured to be installed against a plastic tank with water in it, not against a metal or plastic battery with dense material inside it. The thermostats in them may not cover the temperature range you're looking for (45°F to 68°F)
That same warming pad company that I talked to made a set of pads for me with no thermostat inside the pad and sold an external thermostat to go with it. I found that those thermostats were unreliable and of course, not programmable. I let them know about the problem and provided my data. I did get a response a while afterwards that I wasn't the only one that encountered that problem and they were working on it. I went with a programmable thermostat with a temperature probe that connects to the thermostat. After two years, it's working very well.
Yes, I paid a lot for my pads and their flawed thermostat. But I sleep real good at night when the temperature is below 0°F.
ChillnGrill
Solar Enthusiast
Far too high temp for batteries.
stonematt
New Member
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- Dec 24, 2019
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got mine going today:
we'll see...
https://www.icloud.com/sharedalbum/#B0cG9Gd2NGiCR4p
- controller: https://a.co/ganu3F4
- heating pads: https://a.co/ik88kI5
- wired though this fusebox: https://a.co/80Zzu9Q
we'll see...
https://www.icloud.com/sharedalbum/#B0cG9Gd2NGiCR4p
I did not find proper information regarding what energy is needed to heat up a battery in order to get it to a working temperature. So I did some experiments with my 48V 280Ah battery. With 1kWh I was able to heat it up from 2C to 22C. This is with proper heat insulation (6cm EPS) and in a 24-hour time window.
Let's consider the insulation perfect. The total cell weight is ~90kg. This means that you need ~1W of energy per kilogram of LiFePo4 cells to heat them by 1 degree Celsius.
Now let's consider the information on the internet about the LiFePo4 cells' specific heat energy. The numbers are at ~1000J/kg. Or roughly 0.3W per kilogram of cells to heat them up by 1 degree Celsius. Looks likely the insulation I have is far away from perfect.
This should give a rough estimate of the required heating time with a specific heating pad. I guess this would be useful when somebody is trying to decide what heating element is needed for his case.
Let's consider the insulation perfect. The total cell weight is ~90kg. This means that you need ~1W of energy per kilogram of LiFePo4 cells to heat them by 1 degree Celsius.
Now let's consider the information on the internet about the LiFePo4 cells' specific heat energy. The numbers are at ~1000J/kg. Or roughly 0.3W per kilogram of cells to heat them up by 1 degree Celsius. Looks likely the insulation I have is far away from perfect.
This should give a rough estimate of the required heating time with a specific heating pad. I guess this would be useful when somebody is trying to decide what heating element is needed for his case.
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